1. Technical Field
The present disclosure relates to endotherm systems and methods that employ one or more carbohydrates in a non-oxidizing (i.e., low oxygen) environment to absorb and/or dissipate heat from a potentially heat sensitive environment. Exemplary embodiments and implementations of the disclosed systems and methods employ one or more carbohydrates in combination with an oxygen scavenger to provide thermal control and/or thermal protection to heat sensitive devices and/or components, e.g., electrical devices and the like.
2. Background Art
Active cooling of electronic components, particularly delicate TR modules, Impatt diodes, data recorders, containers for chemicals and munitions, batteries and the like, is not always feasible. Even when feasible, active cooling generally requires continuous high energy cooling, which taxes other ancillary engineering systems typical in missiles, aircrafts, railroads, trucks, automobiles, guns, nuclear reactor systems, related combat systems, as well as commercial systems and technology.
The heat sinks of the prior art generally employ phase change material compositions (PCMs) for the absorption and dissipation of heat. Conventional PCM materials are largely solid or fluidic in nature, i.e. liquids, quasi-liquids or solids such as waxes or other meltable compositions. However, these conventional PCMs have proven to suffer from many technical problems, as well as problems in their use and application. These problems include relatively low latent heats of fusion, the inability to control the shape and form of such fluid PCM materials, as well as the unevenness of heating and cooling. Other problems include the need to provide a containment housing and the stress placed on the housing, resulting in frequent rupture and spillage of the PCM, potential hazards to life and property due to high heat content and flammability of conventional PCMs, and uneven cooling hysteresis. In addition, the use of such known PCMs can lead to spillage of hot fluids onto a human's skin, resulting in serious third degree burns due to the sticky contact nature of many hot wax and polymer or plastic PCMs. Ruptured non-composite fabric endothermic material (CFEM) or liquefied bulk PCM disks may spill their content and cause flash fires, which have a tendency to spread as the PCM pours out during heating in ovens Moreover, wax-filled disks are prone to fires which can spread and flow out of stoves.
Applicant has addressed some of these and other PCM problems in his U.S. Pat. No. 4,446,916, disclosing composite fabric endothermic materials (CFEMs) and providing devices especially suitable for use as heat sinks for aerospace and military use. The disclosed CFEMs provide an improved heat sink that absorbs heat at the melting temperature of a compound embedded within a fibrous mesh or matrix. The CFEM preferably includes a phase change material which is held by capillary action and chemical adhesion to the fibers of the matrix. As a result, a greatly increased surface area for heat transfer is obtained, thus providing for controlled melting and thermal dissipation of the fusion cooling agent.
Applicant has also addressed some of the PCM problems in U.S. Pat. No. 5,709,914, which addresses the need for an improved recyclable endothermic/exothermic thermal storage method for use in many commercial and civilian applications, e.g., in food, home and commercial packaging operations. In the '914 patent, improved CFEMs are disclosed that are capable of being employed in a variety of commercial applications, such as in the food industry, where a need has arisen for heat retaining or heat insulating containers, packages and thermal storage devices. However, the active agents disclosed in the '914 patent are not useful in certain heat absorbing devices, as they function simultaneously as endotherms and exotherms. While the agents disclosed in the '914 patent can accomplish some protection from high temperatures through absorption of their latent heat of fusion, such agents are totally unsuitable for applications relating to the absolute protection of heat sensitive devices from high heat. After all, the heat they have absorbed, they must release. In addition, the active agents of the '914 Patent and other prior art PCMs are not capable of absorbing more than 130 cal/gm. Thus, they can remove heat for only a short period of time relative to mass and only at temperatures not exceeding 326° F. Consequently, they are not effective for applications requiring cooling at very high temperatures and for long periods of time as would be needed, for example, in airplane and railroad crash recorders, missile electronics, spacecraft devices, power supplies, data recorders employed as aircraft and railroad components and combat devices, and in commercial uses such as oven sensors, fire walls, nuclear reactors, munitions' boxes, chemical containers, batteries and automobile exhaust systems. Finally, the agents disclosed in the '914 patent tend to burn at relatively high temperatures, raising the overall heat content of the system.
More recently, applicant has issued a series of patents directed to advantageous endotherm systems that provide non-reversible heat absorbing applications. For example, applicant has disclosed heat absorbing devices and methods capable of absorbing heat for the cooling and maintenance of the temperature of heat sensitive devices at acceptable levels. [See U.S. Pat. Nos. 6,793,844; 6,780,345; 6,773,623; 6,759,476; 6,673,260; 6,652,770; 6,638,444; 6,558,568; 6,264,854; 6,261,475; 6,241,910; 6,241,909; 6,238,591; 6,235,216; and 6,224,784; the contents of the foregoing U.S. patents are incorporated herein by reference.] The disclosed endothermic agents include certain acids and their salts, certain bases and their salts, certain hydrate salts and certain organic compounds. The disclosed endothermic agents are effective in absorbing large quantities of heat to decompose to their individual component elements at temperatures specific to such agents. Additional heat may be absorbed by the disclosed endothermic agents, e.g., in connection with phase change phenomena and/or dehydration. Exemplary endotherms include boric acid; metal hydroxides and their mixtures; carbonates and bicarbonates and their mixtures; salts of acetic acid, salts of formic acid, salts of boric acid and their mixtures; paraldehyde, paraformaldehyde and trioxane and their mixtures; and hydrate salts and their mixtures. The endothermic systems and methods disclosed in these prior patents are effective and have been utilized in commercial systems to achieve desired levels of thermal control and/or thermal protection.
Nonetheless, a need remains for improved systems and methods for providing thermal control and/or thermal protection, e.g., for electronic devices and the like. The need extends to the thermal protection of various heat sensitive devices, such as airplane and railroad crash recorders, missile electronics, munitions boxes, clothing, firewalls, safe boxes, nuclear reactors, laser shields, thermal pulse shields, spacecraft devices, power supplies, data recorders employed as aircraft and railroad components, combat devices, as well as in commercial uses such as oven sensors and the like. These and other needs are satisfied by the systems and methods disclosed herein, as well be apparent to persons of skill in the art from the disclosure that follows.